Is Pulmonary Capillary Wedge Pressure a Reliable Indicator of Postcapillary Pulmonary Hypertension?

Although current pulmonary hypertension (PH) guidelines recommend a pulmonary capillary wedge pressure (PCWP) >15 mm Hg for the detection of a postcapillary component, the rationale of this recommendation may not be quite compatible with the peculiar hemodynamics of PH. We hypothesize that a high PCWP alone does not necessarily indicate left-sided disease, and this diagnosis can be improved using left ventricle transmural pressure difference (∆ P_TM). In this 2-center, retrospective, observational study, we enrolled 1,070 patients with PH who underwent heart catheterization, with the final study population comprising 961 cases. ∆ P_TM was calculated as PCWP minus right atrial pressure. The patients with group II PH had significantly higher ∆ P_TM values (12.6 ± 6.6 mm Hg) compared with the other groups (1.1 ± 4.8 in group I, 12.4 ± 6.6 in group II, 2.5 ± 6.4 in group III, and 0.8 ± 8.0 in group IV, p <0.001) despite overlapping PCWP values. A ∆ P_TM cutoff of 7 mm Hg identifies left heart disease when PCWP is >15 (area under curve 0.825, 95% confidence interval 0.784 to 0.866, p <0.001). Five-year mortality was significantly higher in patients with high ∆ P_TM and PCWP subgroups compared with low ∆ P_TM plus high PCWP (26.1% vs 18.5%, p = 0.027) and low ∆ P_TM and PCWP subgroups (26.1% vs 15.6%, p <0.001). ∆ P_TM has supplementary discriminatory power in distinguishing patients with and without postcapillary PH. In conclusion, a new approach utilizing ∆ P_TM may improve our understanding of PH pathophysiology and may identify a subpopulation that may potentially benefit from PH-specific treatments.